A browser can generate a mathematically correct left-channel signal.
It cannot tell me whether the speaker on my left actually played it.
That distinction sounds obvious, but it changed the architecture of a browser audio tool I was building. A straightforward implementation can create an oscillator, pan it left or right, and display a reassuring success state. The signal graph is correct, so the test looks complete.
Now consider a pair of speakers connected the wrong way around.
The browser would still report success. The user would hear the “left” signal from the physical speaker on the right. A loose cable, an operating-system balance setting, a Bluetooth profile change, or a damaged driver would create similar gaps between the digital graph and reality.
